The present invention relates to a foam earplug and more specifically to a foam earplug with a non-permeable elastomeric coating.
In the prior art, foam earplugs have been made of a slow recovery resilient foam material and such slow recovery earplugs have gained wide acceptance. As an example, an earplug as shown and described in U.S. Pat. No. RE29487 is used by rolling the earplug down to a small diameter and then inserting the rolled earplug into the ear. The earplug is then allowed to expand over a period of time, generally between a few seconds to as much as about a minute, to fill a substantial portion of the user's ear canal.
Slow recovery earplugs may be made by a variety of techniques. One method of manufacturing is to punch out cylindrical earplugs from a sheet of slow recovery material. A second method of manufacturing is to mold in a closed or open cavity mold earplugs in a desired shape. As an example, a molded earplug is shown in U.S. Pat. No. 4,774,938. This patent also demonstrates that a molded plug will typically have smaller cells at the surface of the earplug since the molding process would tend to compress the cells at the surface. Whether the earplug is formed by cutting out of a sheet or by molding within a cavity, the outer surface is porous and allows the escape of air.
In the prior art, there are also earplugs that have been designed that use a combination of an outer shell or bag and with some sort of sound absorbing material such as a foam or fibrous material maintained within the shell or bag. Examples of earplugs that have an outer relatively thick shell are shown by U.S. Pat. Nos. 4,461,290, 2,441,866 and 2,672,863. Examples of earplugs that have an outer bag are shown by U.S. Pat. Nos. 4,160,449, 3,771,521 and 4,498,469. Some of these patents have the inner sound absorbing material formed by a foam and some by fibrous material but in both cases the outer shell or bag is formed as a separate member and it does not have the characteristics of being a close intimate skin or coating bonded on the surface of the foam earplug.